title: Neuroanatomical and neurochemical organization of projections from the central amygdaloid nucleus to the nucleus retroambiguus via the periaqueductal gray in the rat.
abstract: The periaqueductal gray (PAG)-nucleus retroambiguus (NRA) pathway has been known to be involved in the control of vocalization and sexual behavior. To know how the amygdaloid complex influences the PAG-NRA pathway, here we first examined the synaptic organization between the central amygdaloid nucleus (CeA) fibers and the PAG neurons that project to the NRA by using anterograde and retrograde tract-tracing techniques in the rat. After ipsilateral injections of biotinylated dextran amine (BDA) into the CeA and cholera toxin B subunit (CTb) into the NRA, the prominent overlapping distribution of BDA-labeled axon terminals and CTb-labeled neurons was found ipsilaterally in the lateral/ventrolateral PAG, where some of the BDA-labeled terminals made symmetrical synaptic contacts with somata and dendrites of the CTb-labeled neurons. After CTb injection into the lateral/ventrolateral PAG, CTb-labeled neurons were distributed mainly in the medial division of the CeA. After BDA injection into the lateral/ventrolateral PAG, BDA-labeled fibers were distributed mainly in and around the NRA within the medulla oblongata. Using a combined retrograde tracing and in situ hybridization technique, we further demonstrated that more than half of the CeA neurons labeled with Fluoro-Gold (FG) injected into the lateral/ventrolateral PAG were positive for glutamic acid decarboxylase 67 mRNA and that the vast majority of PAG neurons labeled with FG injected into the NRA expressed vesicular glutamate transporter 2 mRNA. The present results suggest that the glutamatergic PAG-NRA pathway is under the inhibitory influence of the GABAergic CeA neurons.
authors.affiliation: Department of Anatomy and Morphological Neuroscience, Shimane University School of Medicine, Izumo 693-8501, Japan.
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Oka
authors.forename: Toshiko
authors.initials: T
authors.lastname: Tsumori
authors.forename: Shigefumi
authors.initials: S
authors.lastname: Yokota
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Yasui
mesh_terms: D000344:Afferent Pathways / Q000502:physiology / Q000648:ultrastructure; D000679:Amygdala / Q000166:cytology* / Q000378:metabolism*; D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives / Q000378:metabolism; D002772:Cholera Toxin / Q000378:metabolism; D003911:Dextrans / Q000378:metabolism; D007839:Functional Laterality; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000378:metabolism; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology* / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure; D010487:Periaqueductal Gray / Q000166:cytology* / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D050599:Vesicular Glutamate Transport Protein 2 / Q000235:genetics / Q000378:metabolism
chemical_list: D003911:Dextrans; D050599:Vesicular Glutamate Transport Protein 2; C076397:biotinylated dextran amine; D001710:Biotin; D002772:Cholera Toxin; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1